Add a heading and link for search re-indexing

Will need this link for documentation on search trouble-shooting
Add link to OOM and info for other process heaps

This will be linked from the documentation on omero.search.batch
referencing the fact that the heap size may need to be increased if the
batch size is increased.
Add sections for omero.search config settings
Add target to link to IceGrid admin tools

This will be used in the troubleshooting section on the Indexer
Add comment on potentially corrupting search index
Add section on search indexer troubleshooting

This section contains a series of steps that sysadmins should take in
attempting to resolve a situation where search is not returning the
correct results. It also references previously updated/modified sections
on the new search configuration settings and increasing the indexer's
heap size.
Style edits to server advanced config file
Proofing/wording edits to troubleshooting
Merge pull request #684 from jballanc/rebased/develop/11995

Update documentation for search indexer and related troubleshooting steps (see #11995) (rebased onto develop)