Improve input method configuration

As was reported in some places, such as the following:

• Keyboard accent error in trisquel 9 mate desktop
• #7777: Adding ibus Input Method Breaks Accents in Spanish Input
• #11999: GNU Cash: some keyboard keys don't work
• #13138: Nautilus eventually rejects most keyboard input
• #14775: cannot switch Between two keyboard layouts with shortcuts
• #14904: Diacritics suddenly stop working Asignado a: leny2010
• #18116: typing
• #19689: Changing keyboard layout does not work

… the default input method configuration causes some issues, ranging from inability to switch languages, to lack of accents support.

A proposed workaround, for each user who has a graphical login session, is as follows:

1. make a text file called .xinputrc at the user's home, and insert only the following in the file:

   run_im xim

2. create another text file on user's home called .xprofile with the following content:

   unset GTK_IM_MODULE
   export XMODIFIERS="@im=none"

3. log out and then back in, this should fix the accents;
4. optionally, if you must use two layouts, now you can go to Trisquel logo, “System”, “Preferences”, “Hardware”, “Keyboard” (mate-keyboard-properties, as of Trisquel 9), “Layouts”, and from here you can add other layouts, and under “Keyboard model”, clicking on “Options” and going to “Change to other layout”, select the key you want to perform the changes.

What is needed now is for a way for Trisquel to implement the needed file changes as stated on steps 1 and 2. Perhaps placing them on /etc/skel, could help for new installs of future releases.