dwarftherapist starter script rewrite

changed categories in .desktop file.

rewrote dwarftherapist starter script:
- set all paths in variables so installer scripts may easy "sed" them
- catching most common errors and give feedback even if not run by terminal (bin/etc not found, ptrace active)
- provide simple gui for "setcap cap_sys_ptrace=eip"
- no more sudo if cap_sys_ptrace=eip is set to DwarfTherapist

tested on Mint 17, Debian wheezy and Arch