Drumrox 2.1.0 + 3 drumkits (Lel PSR, Lel DR8, LinnDrum)

Hello!
Besides many fixes and code refactoring, there are some interesting new features.

1. First of all, I've made a [Drumrox site] (https://psemiletov.github.io/drumrox/) which is more clear as the github's project page.

2. Also, here is a repository for [Drumrox kits] (https://github.com/psemiletov/drumrox-kits). Yes, Drumrox 2.1 introduces, in addition to Hydrogen format support, the new drumkit format. Hydrogen is a larger program than Drumrox, so it needs more complex format with wide set of features. Instead of that, Drumrox provides simple format in the form of directory, which contains the samples and drumkit.txt file. The last one looks like that:

Snare=snare.wav
Crash=crash.wav

So we can quickly create and use new kits.

3. Currently at the Drumrox kits repo are 3 kits, let me introduce them! Lel PSR - the legendary Soviet drum machine, used at early albums of famous USSR rock bands such as Kino, Strannye Igry, Aquarium. Lel DR8 - the continuation of Lel PSR. LinnDrum - drum machine manufactured by Linn Electronics between 1982 and 1985.
   LinnDrum was used by Peter Gabriel, Stevie Wonder, Gary Numan, Michael Jackson, Devo, John Carpenter, Prince, Madonna, Elton John, Queen (at Radio Ga Ga).

4. Search paths for drumkits are:

/usr/local/share/hydrogen/data/drumkits
/usr/share/drmr/drumkits
/usr/share/drumrox-kits
$HOME/.hydrogen/data/drumkits
$HOME"/.drmr/drumkits
$HOME/.drumrox/drumkits
$HOME/drumrox-kits

5. Drumrox kit can have the picture (named "image.png") of drum machine/kit, that appears at plugin window.

6. Future plans - porting GUI part from GTK2 to another kit (Nuklear? FLTK?), fixes, rewritting some code that I hardly understand, etc. More new kits!