Define and use event identifiers

* VuFindSearch/Service.php (EVENT_PRE, EVENT_POST, EVENT_ERROR,
EVENT_RESOLVE): Define constants for event identifiers.
(triggerPre, triggerPost, triggerError, resolve): Use event
identifiers.
Add VuFindSearch event namespace

* VuFindSearch/Service.php (setEventManager): Add `VuFindSearch' event
namespace, following common zf2 pattern.
Simplify lazy-loading new event manager

* VuFindSearch/Service.php (getEventManager): Simplify lazy-loading
new event manager.
Remove unused logger dependency

* VuFindSearch/Service.php ($logger, setLogger, log): Remove unused
logger dependency.
* ../Module.php (setup): Dto.
Use VuFindSearch event namespace

* VuFind/Bootstrapper.php (Bootstrapper): Use VuFindSearch event
  namespace.
Add search system invokable configuration
Remove VuFindSearch service setup functions

* ../Module.php (getServiceConfig, setup): Removed. Service is an
invokable.
Mark CitationTest skipped if short_open_tags is disabled

Mark test skipped if short_open_tag is not enabled. The partial uses
short open tags. This directive is PHP_INI_PERDIR, i.e. can only be
changed via php.ini or a per-directory equivalent. The testCitations()
will fail if the test is run on a system with short_open_tag disabled
in the system-wide php ini-file.
Merge pull request #22 from dmj/t/search-2.1

Minor improvements for release 2.1 (mostly search system related)
Resolving VUFIND-874 (Undefined Notice if User Browser agent is empty in statistics).
Style fix.
Added trimming of slashes/whitespace to query builder.
Cleaned up comments.
Add support for ->saveCredentials VUFIND-867
Added support for the cat_password attribute to be pulled from Shibboleth Attributes.
Resolves VUFIND-866; thanks to Tom Misilo for much of the code.
Expanded Welsh translation (thanks to Luke O'Sullivan).
Updated Portuguese translation from Filipe Bento.
Updated package files.
Fixed version number in config.
Improved .deb package with CLI cache prep.