MODE-2339: Inject repository connector via <context-param> element

[okulikov]

This PR implements approach for loading repositories:

• should specify container specific implementation of the Connector class;
• if is unspecified then default WF-compatible Connector will be loaded.

[hchiorean]

@okulikov: this change is fine, but it still doesn't allow users to easily specify the JNDI name.
Using different connector implementations is fine, but then IMO we need to at least:
a) have a connector which is able to load repository JSON files (i.e. single repositories)
b) allow the JNDI name to be configurable - not hardcoded to jndi:jcr like in the current ConnectorImpl

[okulikov]

@hchiorean , regarding b)
do you mean to extend the current, 'default' connector with configuration properties?

[hchiorean]

@okulikov: yes, where the configuration comes from the web.xml in some way (maybe another <context-param>) The reason is that the web.xml is the main/only file users should have to overlay/edit for their own applications.

[okulikov]

Next commit provides:

• ability to configure jndi name where to look up engine;
• another connector implementation which is able to deploy repository from json configurarion file

[hchiorean]

looks good.
@okulikov can you please also update the modeshape-web-explorer-war module and test the JSON file connector ? (most likely adding some test resources - i.e. a repository JSON file & a test web.xml which contains the configuration)
Not sure if it's possible but ideally the ExplorerTest test case would then validate that this repository is accessible by accessing the repository "URL" (if there is such a thing, I'm thinking something along the lines of http://localhost:8090/modeshape-explorer/<repo>).
We also need to document these configuration options, but I'm not sure what the best approach is (we don't have any explorer documentation as of yet).
@rhauch thoughts ?

[rhauch]

@hchiorean, perhaps a new page for the Explorer under https://docs.jboss.org/author/display/MODE40/ModeShape+Guide?

[hchiorean]

@rhauch maybe a new page under https://docs.jboss.org/author/display/MODE40/Using+ModeShape ? (which contains the REST & WebDAV pages)

[rhauch]

@hchiorean, sure, that's fine.

[hchiorean]

@okulikov: can you pls add this and document the configuration aspects once this PR is merged

[okulikov]

Pushed small commit with fix for several errors. Test case still a bit an issue due to ajax nature of application. It always returns same page with reference to java script.

[hchiorean]

@okulikov see the above comments
For the test if there's no URL we can use to actually test the fact that the repository is accessible, I'm fine with leaving that as-is; i.e. unchanged

[okulikov]

@hchiorean pushed commit with transient fields. missed it.

[okulikov]

@hchiorean , regarding test I am trying to find something what we can catch to decide is it right test or failed.

[hchiorean]

@okulikov after finishing updating the test, pls squash the commits & update this PR. thanks

[hchiorean]

@okulikov any update on this ? As mentioned above, if finding a "static" link to test the repository is too difficult (thanks to GWT..) this PR is fine as is (just needs squashing)

[okulikov]

@hchiorean , one more try to catch something for check inside java script and then I will squash either with test or as is.

[okulikov]

@hchiorean , just squashed commits