Fixed /usr/locl/bin/perl -> /usr/bin/perl for centos
Fixed FindBin error after relocation
Added missing tusk.search_result% tables to tusk.sql
removed Ovid from pubMed text
Project to remove Tusk internal Ovid externam content linking

1) Removed Ovid rows from the 'content_external_source' table
2) Remove OVID module and subdirectories.
3) Move and renamed Medline -> PubMed module
4) Added core Plugin.pm module to handle future external content linking plugins.
5) Modified Source.pm and PubMed.pm modules to support plugins.
Upgrade instructions for missing search tables and new pubmed
Merge branch 'origin/jpb-opentusk-pubmed' into opentusk

This change updates external content linking to support
plugins.

Put in missing files that broke search.

Change Perl executable to /usr/bin for CentOS.
XSL with eval info will now display preliminary due date as the due date as long as it's set
Remove unused file bin/fts_umls_index

UMLS indexing is done by bin/fts_index.
removed redundant (and incorrect) setting of HOSTNAME, DATABASE_ADDRESS, HSDB_DATABASE_USER, HSDB_DATABASE_PASSWORD in tusk_base.conf that overwrote previous declarations
Fix mason.pl startup constants [TUS-2386]

Old version was using %ENV that relied on them being set
in Apache config. New version uses TUSK::Constants and so
is always consistent with tusk.conf.

Change die to confess in checking sections to get useful
stack trace and line numbers.

Change unless to if (Perl Best Practice 66). Also because
nested unless kills unicorns.
Add min-height to footer so icon will display properly [TUS-2495]
Fix formatting of bin/fts_index [TUS-2450]

Make whitespace consistent with Perl Best Practices.
Change usage message to heredoc.
Run with /usr/bin/perl by default.
Fixup bin/fts_index styles, readability, consistency [TUS-2450]
Add command line option `help' to bin/fts_index [TUS-2450]
Add comments and minor formatting updates to bin/fts_index [TUS-2450]
Consolidate index_content_id_all into index_content_id [TUS-2450]

Add default parameters to index_content_id for more
modular behavior.
index_content_id(..., {die_on_failure => 0}) will emulate
behavior of deleted method index_content_id_all.
Fix formatting in TUSK::Services::MMTx->find_concepts [TUS-2450]
Add test count to t/tusk_conf.t [TUS-2450]
Wrap MMTx call in eval for timeout in TUSK::Services::MMTx [TUS-2450]