Improve documentation for C3p0JdbcConnectionProvider

There does not seem to be good documentation for the subject.properties values used for the C3p0JdbcConnectionProvider provider, despite it being the stated default for jdbc connections. Most examples in the wiki and subject.properties examples mention c3p0, but end up using GrouperJdbcConnectionProvider which has different defaults.

The parameter names "maxActive" and "maxWait" are not explained and are not shown the defaults.

Param maxActive is the c3p0 maximum pool size. The default (hard-coded in JDBCSourceAdapter2) is 2.

Param maxWait is the c3p0 checkout timeout in seconds. The default is 5 seconds (hard-coded in JDBCSourceAdapter2). The example sources.xml in the wiki sets it to -1, which is a bad example because it causes it to default to 5 minutes.

Param dbDriver is required, and will throw an NPE if not defined. It is only needed to force a driver load; however, all the drivers are already loaded as part of the Grouper startup. It is only in the wiki as a subject.properties value one time inside an example config. It is mentioned a few times in older sources.xml example configs.

Other params that can be configured but have no mentions in the wiki or example configs:

• maxConnectionAge
• testConnectionOnCheckout
• preferredTestQuery
• idleConnectionTestPeriod