Add footprint select dropdown to component chooser, serious refactoring

- DIALOG_CHOOSE_COMPONENT has footprint select widget
- FOOTPRINT_SELECT_WIDGET
- FOOTPRINT_CHOICE widget (customized wxComboCtrl)
- FOOTPRINT_FILTER class
- FOOTPRINT_INFO rework:
    - FOOTPRINT_ASYNC_LOADER to load without freezing UI
    - Rewrite loader threads as queue-driven thread pool
    - Make FOOTPRINT_INFO available via kiway
- FP_LIB_TABLE::PrefetchLib
- Access to global fp-lib-table via kiway
- SYNC_QUEUE threadsafe queue template
- Remove KICAD_FOOTPRINT_SELECTOR build option

common/eda_pattern_match.cpp

@@ -34,6 +34,12 @@ bool EDA_PATTERN_MATCH_SUBSTR::SetPattern( const wxString& aPattern )
 }
 
 
+wxString const& EDA_PATTERN_MATCH_SUBSTR::GetPattern() const
+{
+    return m_pattern;
+}
+
+
 int EDA_PATTERN_MATCH_SUBSTR::Find( const wxString& aCandidate ) const
 {
     int loc = aCandidate.Find( m_pattern );
@@ -75,6 +81,12 @@ bool EDA_PATTERN_MATCH_REGEX::SetPattern( const wxString& aPattern )
 }
 
 
+wxString const& EDA_PATTERN_MATCH_REGEX::GetPattern() const
+{
+    return m_pattern;
+}
+
+
 int EDA_PATTERN_MATCH_REGEX::Find( const wxString& aCandidate ) const
 {
     if( m_regex.IsValid() )
@@ -100,6 +112,8 @@ int EDA_PATTERN_MATCH_REGEX::Find( const wxString& aCandidate ) const
 
 bool EDA_PATTERN_MATCH_WILDCARD::SetPattern( const wxString& aPattern )
 {
+    m_wildcard_pattern = aPattern;
+
     // Compile the wildcard string to a regular expression
     wxString regex;
     regex.Alloc( 2 * aPattern.Length() );   // no need to keep resizing, we know the size roughly
@@ -132,6 +146,12 @@ bool EDA_PATTERN_MATCH_WILDCARD::SetPattern( const wxString& aPattern )
 }
 
 
+wxString const& EDA_PATTERN_MATCH_WILDCARD::GetPattern() const
+{
+    return m_wildcard_pattern;
+}
+
+
 int EDA_PATTERN_MATCH_WILDCARD::Find( const wxString& aCandidate ) const
 {
     return EDA_PATTERN_MATCH_REGEX::Find( aCandidate );