Created initialization function for Core-specific configuration variables

Similar to commit 3268e72f51b22e0780ef0f74f90d7bb9f5d610a1, this commit
creates an initialization function for Core-specific configuration
variables. As with the aforementioned commit, depending on the code
execution path, there was previously the possibility of attempting to
free a pointer variable whose value was pointing to something in the
data segment. This commit fixes that.

Additionally, previously the variables were being initialized in two
places: when they were declared and in the reset_variables() function.
In several cases they were initialized differently and that difference
has been maintained. Whether they should be initialized differently
should still be determined. For any variables that were being initialzed
the same in both places, they are now only initialized once.
Scheduling: Added macros for min and max nugde values

Nudge values are used to move service checks ahead in time when the
maximum number of parallel service checks has been exceeded. This
commit creates macros for the min and max nudge values and thus rids
the world of two more undocumented numeric constants.
Fix bug in check_window() macros

This commit corrects the logic in the check_window() macro so that
the macro returns the retry interval when the object (host or service)
is in a non-OK soft state and the check interval otherwise. Previously
it was returning the retry interval only when the object was in a soft
OK state meaning that checks for objects in OK states were happening
more often than necessary and checks for objects in non-OK states
weren't happening as often as they should.
Tests: test_events once again passes all tests
Fix bug #596 (duplicates #590, #586): SIGSEGV crashes in CGIs.

If contact is not defined in authorized_for_all_hosts directive of cgi.cfg
and authorized_for_all_hosts is not *, most CGIs die with SIGSEGV.

is_contact_for_host_escalation() was referencing a NULL-initialized temporary
instead of the hostescalation argument. Correct the references, remove the
temporary, and add an argument check.

(Alexey Dvoryanchikov)
Tests: test_downtime once again passes all tests
Update .gitignores to clean up git status output
Tests: test_nagios_config once again passes all tests
Object JSON: Added values of custom variables

This commit adds the values of custom variables to the details of hosts,
services and contacts displayed using the object JSON CGI.
Merging master.
Fix #608: Service check timeout output string has an unnecessary extra newline.
Fix #609: Image on home page doesn't have correct image path prefix.
Fix bug #496: Syntax error in exfoliation's common.css.
Merge branch 'master' of https://github.com/NagiosEnterprises/nagioscore