convert/main: moved set_verbosity for bug #262

set_verbosity is now called directly after parsing args
engine/terrain: made structs out of blendmode and terrain classes
openage/init: prettier initial terrain with beaches
convert: only read files if needed (for bug #263)

now calling get_file_data() only if write_enabled is true
engine/terrain: renamed current terrain class to terrain chunk
convert: parsing args in seperate function
convert: renamed args.extractionrules

args.extractionrules wasn't a parsed argument, but created later.
Renamed it to extraction_rules.
convert: split util.set_dir into two functions

Replaced by util.set_read_dir and util.set_write_dir
readme: added gcc 4.8 or clang 3.3 dependencies
Merge branch 'convert' of https://github.com/zuntrax/openage into merge-tmp