Updated configuration loading

* The getLocaleResolver method now uses the getConfigurationLoader
method to retrieve the configuration loader instead of directly using
the StandardConfigurationLoader
* Fixed the group resolution when there is no user properties
* Improved logging
* Removed dead code in TableConfiguration
* Removed the JstlMessageResolver from the default properties because
there is no JSTL jar when using the Thymeleaf module... The user
properties is now dynamically updated to set the default
JstlMessageResolver if the JSTL jar is present in the classpath and if
no custom message resolver is configured
* Linked with dandelion/issues#4 and dandelion/issues#113
New Spring message resolver

* Linked with dandelion/issues#4
* ConfigurationLoader and implementations now need the
HttpServletRequest to initialize the MessageResolver properly if it is
configured
* Added comments
Optimization in the message lookup

The ColumnTag#doEndTag() method has been refactored to lookup the
message (for the column's title) only at first iteration
Global group is now stored and returned when using empty group

Closes dandelion/issues#139
Added empty constructor required by Spring

Linked with dandelion/issues#4
Fixed typo in comment
Improved logging during configuration loading

* Added unit tests for StandardConfigurationLoader
* Take into account the i18n.locale.resolver during the group resolution
* Removed dead code/files
* Linked with dandelion/issues#113