CMessageHeader sanity changes

- Remove spurious `pchCommand[1] = 1` in CMessageHeader()
- Make sure that pchCommand is zero-padded if length is shorter than
  COMMAND_SIZE
- Use strnlen to determine length of pcmCommand in GetCommand
minor variable init changes in init.cpp

- explicit init of pcoinsdbview and pwalletMain (even if not needed, as
  globals are init to NULL, it seems cleaner)
- remove check if (pwalletMain) in Shutdown() as delete is valid even if
  pwalletMain is NULL

Conflicts:
	src/init.cpp
LLu is standard, but not portable. use ULL
Disable App Nap on OSX 10.9+

Conflicts:
	share/qt/Info.plist.in
move CTxIn and CTxOut into core