Update INSTALL & README* files

INSTALL

@@ -285,12 +285,17 @@ List of supported parameters (passed as -DPARAMETER=VALUE):
 | ENABLE_QT            | bool | ON      | Build Qt frontend
 | ENABLE_WIN           | bool | ***ON   | Build Windows native frontend
 | ENABLE_THEORA        | bool | **ON    | Support video capture to OGG Theora
+| ENABLE_TOOLS         | bool | OFF     | Build tools for Celestia data files
+| ENABLE_TTF           | bool | ****OFF | Build with FreeType support
+| NATIVE_OSX_APP       | bool | OFF     | Support native OSX data paths
 
 Notes:
  * /usr/local on Unix-like systems, c:\Program Files or c:\Program Files (x86)
    on Windows depending on OS type (32 or 64 bit) and build configuration.
+   This option effect is overriden by NATIVE_OSX_APP.
  ** Ignored on Windows systems.
  *** Ignored on Unix-like systems.
+ **** This option support is not finished yet.
 
 Parameters of type "bool" accept ON or OFF value. Parameters of type "path"
 accept any directory.

README

@@ -27,6 +27,7 @@ CONTENTS
   Known Issues
   User Modifiable Elements
   Celestia Resources
+  Building From Sources
   Contributions
   Acknowledgements
 
@@ -200,6 +201,17 @@ Celestia Bug Tracking:
 Celestia Feature Requests:
   https://github.com/CelestiaProject/celestia/issues
 
+Celestia Discord Server:
+  https://discordapp.com/invite/WEWDcJh
+
+Celestia SubReddit:
+  https://www.reddit.com/r/Celestiasoftware/
+
+
+BUILDING FROM SOURCES
+---------------------
+See file INSTALL for building instructions.
+
 
 CONTRIBUTIONS
 -------------

README.md

@@ -3,13 +3,15 @@
 |[![GitHub release](https://img.shields.io/badge/Release-v1.6.1-blue.svg)](https://celestiaproject.net/download.html) | [![Localization](https://img.shields.io/badge/Localized-85%25-green.svg)](#) | [![License](https://img.shields.io/badge/License-GPLv2-blue.svg)](https://github.com/CelestiaProject/Celestia/blob/master/COPYING) | [![Contribute](https://img.shields.io/badge/PRs-Welcome-brightgreen.svg)](#contributing) |
 
 # Celestia
-![Celestia](celestia-logo.png)  
+![Celestia](celestia-logo.png)<br>
-**A real-time space simulation that lets you experience our universe in three dimensions.**  
+**A real-time space simulation that lets you experience our universe in three dimensions.**
 
-**Copyright © 2001-2019, Celestia Development Team**  
+**Copyright © 2001-2019, Celestia Development Team**<br>
-**Celestia website: https://celestia.space**  
+**Celestia website: https://celestia.space**<br>
-**Celestia WikiBook: https://en.wikibooks.org/wiki/Celestia**  
+**Celestia WikiBook: https://en.wikibooks.org/wiki/Celestia**<br>
-**Celestia forums: https://celestia.space/forum/**  
+**Celestia forums: https://celestia.space/forum/**<br>
+**Celestia Discord Server: https://discordapp.com/invite/WEWDcJh**<br>
+**Celestia SubReddit: https://www.reddit.com/r/Celestiasoftware/**<br>
 **Celestia Archive Repository: https://github.com/Anthony-B-Russo10/Celestia-Archive**
 ## License
 
@@ -122,6 +124,9 @@ types of catalog files:
 All three types of catalog file are text files that can be updated with your
 favorite text editing program.
 
+### Building from sources
+See instructions in file [INSTALL](INSTALL).
+
 ## Contributions
 | **`Authors`** | **`Contributors`** | **`Documentation`** | **`Other`** |
 |-----------------|---------------------|------------------|-------------------|