Documentation fixes

Changes in this commit:

• Change «`» to «*» for emphasize: following the mark-up conventions

• Change «File Toolbar» to «Main Tolbar» -- was confused (an application without main toolbar...)

  IMPORTANT: This request GUI changes (an improve)

• Some fixes for menu items

  • (upercase) -- this must be started into GUI

  IMPORTANT: I planned to work with the GUI changes (improves)

  • Added shorcuts

• Remove confusion about Gimp or GIMP: Gimp image hose format/Gimp brush format

• Improves for last additions to master

• Fixes to :menuselection:

  IMPORTANT: I request highlighted for :menuselection: tags -- KDE style.