[BioC] Change to getBioC()

[Jeff Gentry]

Hello ...

In the name of aligning getBioC with reposTools, the 'relLevel' argument
to getBioC() has been replaced with a boolean argument 'develOK', which
defaults to FALSE.

Users who wish to only receive release level software can either just use
the default value or specify 'develOK=FALSE' instead of
'relLevel="release"'.

Users who wish to access developmental packages, data packages, etc will
need to specify 'develOK=TRUE'.

As an example, to download the developmental versions of the 'affy' target
in getBioC:

getBioC("affy", develOK=TRUE)

Or, to stay with all release level software:
getBioC("affy")
or
getBioC("affy", develOK=FALSE)

Please contact me with any questions, concerns or problems.

Thanks
-Jeff