short-circuit -> direct binding
only set the direct binding property if not explicitly provided
XD-1885: Introduce 'hidden' options
XD-1751 Connection Pool settings for jdbc modules

* Includes common pool settings as well as tomcat enhanced attributes
* Initial size is set to zero vs. the default of 10.
* Jdbc Unit has a test for testOnBorrow setting.
* hdfsjdbc, jdbchdfs & filejdbc testing will be covered by acceptance tests
* Code Polishing
Jdbc Connection pool settings now set via yml

Originally the PR used JDBCConnectionPoolMixin in order to set the connection pool settings.  However this proved to be a bit overwhelming for users when trying to setup a jdbchdfs, hdfsjdbc,filejdbc or filesink.
Now the pool setting will be setup via a servers.yml and application.yml
Connection test for shell was removed.

No longer valid, because settings will be established via the .yml files.
Conn Pool Config consolidated to one location in yaml

* Servers.yml
* application.yml
JdbcConnectionPool metadata is now available.

1) Add key datasource and pool variables in servers.yml
2) Add commented out section of datasource and pool variables in modules.yml as an easy way to customize the datasource used for modules but not for the XD infrastructure
3) For any modules that use jdbc functionality, add something like maxIdle = ${spring.datasource.maxIdle} into that module/job property file.
4) investigated to see if there was a way to inject a common snippet of connection pool xml into jdbc.xml, hdfsjdbc.xml, jdbchdfs.xml & filejdbc.  There was no smooth way to do this.
Jdbc Conn Pool autocomplete options are hidden.