Replace certain static with per-instance variables in THaEvData

The static variables fgNeedInit and fgCrateMapName in THaEvData were
previously introduced as a workaround to maintain binary
compatibility. Replace them now with regular member variables. Each
decoder instance obviously has its own init status and, in principle,
may have its own crate map name (although the crate map name is
usually global to the replay).

Also, add a new static function SetDefaultCrateMapName so that we can
still set a global default crate map file name for all decoders
spawned in a given replay. The default is picked up only once at
initialization time, so it currently isn't easy to change crate map
file names in the middle of a replay. Then again, the crate map
business will be rewritten in the upcoming OO decoder (we hope), so
this is good enough for now.

Closes #32
Remove last remnants of external crate map arguments in THaEvData

LoadEvent took as a second argument an optional external crate map
object, which was subsequently simply ignored (although not in an
immediately obvious way). Instead, the decoder automatically generates
and uses an internal crate map fMap. An external crate map is not
useful since the only relevant configuration parameter of the crate
map object is its database file name, which can be set with
THaEvData::SetCrateMapName.

Unfortunately, all derived decoder classes will have to be slightly
changed. Previously, they were required to implement

LoadEvent( const int* evbuffer, THaCrateMap* )

while now they have to provide simply

LoadEvent( const int* evbuffer )

If the external map was used anywhere, fMap should be used instead.
Add fDebug to THaEvData & remove another binary-compatibility workaround

This makes setting the debug/verbosity level of the decoder consistent
with the rest of the analyzer. Previously, for binary compatibility,
two bits had been hijacked to enable verbose mode (now fDebug = 1) and
debug output (now fDebug > 1). Keep SetVerbose function around so we
don't break existing scripts.