Refactored the whole configuration system
The main goal of this refactoring was to increase performance by removing lots of reflection.
 * Added a new ConfigToken allowing to store a configuration, how to read it from properties and how to process it. Note that even if all configurations have been refactored to support the CamelCase, the case remains insensitive when it's read.
 * Added TableConfig and ColumnConfig: placeholder for all possible configurations
 * Refactored ColumnConfiguration and TableConfiguration to use ConfigToken instead of plenty of fields/accessors
 * Improved exception handling when a wrong configuration group was activated
 * Refactored export mechanism to be able to use a totally custom export. Some export formats use reserved words, such as "csv", "pdf", "xml", "xls" and "xlsx" and allow to activate default values (e.g. mimeType, built-in export classes)
 * Refactored all Thymeleaf processor with the new configuration mechanism. Also eased all method signatures thanks to the abstract superclasses.
 * Updated all unit tests
 * Removed the cdn option from the TLD and from the Thymeleaf dialect: it now handled by Dandelion Core
 * Closed dandelion/issues#141 by making some classes implementing the Serializable interface
 * Closes dandelion/issues#191
 * Closes dandelion/issues#176