This fixes issue #46

Squashed commit of the following:

commit 0ee33e3ff89fcd3b5838b6088b23b075fc6bc90e
Author: Nicolai Czempin <nicolai.czempin@gmail.com>
Date:   Thu Apr 3 01:07:23 2014 +0200

    laser shots cost energy

commit 5124503965dcc948c4b8c314c5e694ccba6df208
Author: Nicolai Czempin <nicolai.czempin@gmail.com>
Date:   Thu Apr 3 00:49:26 2014 +0200

    get some fixed starting mass and allow the initial towers to be essentially free.

commit 8c6910a840629cf8a4b0082c01dbfcc3b7673328
Author: Nicolai Czempin <nicolai.czempin@gmail.com>
Date:   Thu Apr 3 00:45:10 2014 +0200

    removing towers increases available mass

commit c29dec0f4a09f1014f6767af19f2856f70b991ea
Author: Nicolai Czempin <nicolai.czempin@gmail.com>
Date:   Thu Apr 3 00:39:24 2014 +0200

    building a tower costs mass

commit 13b07af3bae597cd2d36662c3124db6dc2a9d338
Author: Marcus Ihde <marcusplate@googlemail.com>
Date:   Wed Apr 2 23:06:42 2014 +0200

    Add map cursor

commit bd3ff15640df6b0bb505ab4529d3c25fffb440b4
Author: Nicolai Czempin <nicolai.czempin@gmail.com>
Date:   Wed Apr 2 21:56:38 2014 +0200

    enabled resolution switch and fullscreen toggle

commit fb1d92be07329d9db4364cc68f1534543a8d3e45
Author: Nicolai Czempin <nicolai.czempin@gmail.com>
Date:   Wed Apr 2 21:45:57 2014 +0200

    cleanup

commit 2780fb5910feeef2cca14b3a98c9788b1c0d1eaf
Author: Nicolai Czempin <nicolai.czempin@gmail.com>
Date:   Wed Apr 2 21:45:20 2014 +0200

    switch between small (800x600) and [moderately] large [1280x720) resolutions. this partially fixes issue #54. I will get the fullscreen option setting working too, but actually choosing resolutions from a will be done in a separate issue, because it involves a whole new widget type.

commit bec4c2bad062627f93d29457f5a02a76b221549d
Author: Nicolai Czempin <nicolai.czempin@gmail.com>
Date:   Wed Apr 2 21:34:45 2014 +0200

    Added some additional settings screens and pushed the shader settings
    down. This fixes issue #51

commit 91e0b73b4c982ee67953f4fb2b0ab196dca9e6b8
Merge: 61681ca 9dbdfa0
Author: Nicolai Czempin <nicolai.czempin@gmail.com>
Date:   Wed Apr 2 21:07:35 2014 +0200

    Merge branch 'master' into nczempin

    Conflicts:
    	enemy.lua

commit 61681ca8fb91cf115bccfeea6afbf642a041b634
Merge: 01e179b 3cc0caf
Author: Nicolai Czempin <nicolai.czempin@gmail.com>
Date:   Wed Apr 2 17:35:23 2014 +0200

    Merge branch 'master' into nczempin

    Conflicts:
    	enemy.lua

commit 01e179b514e2269119690376a45c3fb86f0fde9e
Author: Nicolai Czempin <nicolai.czempin@gmail.com>
Date:   Wed Apr 2 17:33:55 2014 +0200

    I meant issue #31

commit 2f1b4c5a0453b257ef339fe4138600f89d09b199
Author: Nicolai Czempin <nicolai.czempin@gmail.com>
Date:   Wed Apr 2 17:09:19 2014 +0200

    here we detect issue #35