Allow `-noserver` with bitcoind

Allow running bitcoind without server.

- Default to -server mode (of course) for bitcoind with SoftSetBoolArg
- Remove fForceServer argument from AppInit2
- Move fDaemon to a static variable in bitcoind
Merge pull request #3449

8b9adca Allow `-noserver` with bitcoind (Wladimir J. van der Laan)