Create working_with_textures.html

started.
Update Resources/Help/Documentation/scripts/commands.js

Added "ArrowKeys" value to keys array.  Just a shortcut for all arrow icons surrounded by ().
Update Resources/Help/Documentation/working_with_textures.html

Finished.

NOTE: Currently divs for the sections are using INLINE STYLE for 'clear:left;'.
Obviously, this is bad and should be added to the stylesheet in a way you see fit.
Merge branch 'master' of https://github.com/necros0/TrenchBroom

Signed-off-by: Kristian Duske <kristian.duske@gmail.com>

Conflicts:
	Resources/Help/Documentation/scripts/commands.js
	Resources/Help/Documentation/working_with_textures.html
Added images and did some cleanup for the "Working with textures" section.

Signed-off-by: Kristian Duske <kristian.duske@gmail.com>