Started merging 2.x branches tasks,emul,crawl:

  * add skeleton of emulator module (emul class)
  * reorganize system modules into subpackages
  * add System, OS, Task and DefineStub classes
  * add AVR architecture
  * modified block class => map attribute moved to cfg.node class
  * moved memory classes in system.memory module
  * moved cfg analysis classes in 'sa' subpackage
  * improve debug logs
  * improve PE/ELF parsers with amoco.structs module
  * add checksec method in Elf class
  * HUGE fix of armv7 semantics and formats