Aux_Plugin class
allow setting section to be defined in child class

PDb_Form_Element
add new filter: pdb-before_display_form_element which passes in the form element object for better control over custom element creation

PDb_List_Query class
fixed issue with saved query getting overwritten by blank non-search query
added FILTER_FLAG_NO_ENCODE_QUOTES flag to FILTER_SANITIZE_STRING in add_filter() encoded quotes ending up in query
build_where_clause() fixed grouping issues with two statement on same field in different groups: grousp can now be set by calling class to control parenthisization
fixed error when adding filter using >= or <=
set_last_of_group_clauses() now more accurately sets last group clause flag with complex series
added public method save_query_session so aux plugin can save the session

List_Query_Filter class
removed string sanitize filters, redundant
change depricated mysql function, now using WP esc_sql() to sanitize inputs.

git-svn-id: https://plugins.svn.wordpress.org/participants-database/trunk@994389 b8457f37-d9ea-0310-8a92-e5e31aec5664