Simplify some of the library editing code. There have been a few minor
changes in the behavior of the editor. If the current symbol is deleted
from the library, the next symbol in the library is not loaded. The
deleted symbol is cleared and the current symbol is empty.
Change component to symbol to align with the preferred terminology
discussed on the developer's mailing list.
Add separate update UI event for save library as to enable the menu entry
whenever a library is selected.
Change the select symbol list dialog to a single column using the LIB_ID
format LIB_NICKNAME:LIB_ITEM_NAME so that the selection can be parsed by
LIB_ID.
Add method to expand URI to LIB_TABLE_BASE.
Override wxApp::OnExceptionInMainLoop() in debug builds to make debugging
easier when an unhandled exception occurs in a wxUpdateUIEvent handler.
Change SCH_SCREENS::HasNoFullyDefinedLibIds() to return false when the
schematic has no symbols to prevent the remapping dialog from being run.
Use SCH_COMPONENT part reference when creating netlist rather than looking
up the library symbol.