can't execute non-lowercase programs

[Hakan Erduman]

Slingshot converts user input to lowercase and fails to execute input if no desktop file is found.

Example:
/usr/local/bin/mbrowse is a program, correctly referenced by /usr/local/share/applications/mbrowse.desktop.

a)
- Remove desktop file, enter mbrowse in slingshot, hit enter
- Runs correct program
(expected behavior)

b)
- rename mbrowse to mBrowse (note casing), enter mBrowse, hit enter
- prints (lowercase) mbrowse in display while typing, executes nothing.
(failure)