- Implemented A3::extract_pattern.
- Implemented A3::infix, which inserts 'and' operators where necessary
in expressions.
- Began implementation of A3::expand which converts old-style filters
(pri:H) to the new algebraic style (priority = H).
- A3 now tracks whether a command is read-only, and builds filters accordingly.
- Implemented extract_filter, extract_modfications and extract_words stubs.
- Removed all E9 implementation details - this is going to be written from
scratch.
- Created A3.{h,cpp} which will be a simpler, lightweight version of
Arguments.{h,cpp} that does less, but does it better.
- Created E9.{h,cpp} which will be a better implementation of
Expression.{h,cpp} that does less, but does it better.
- Integrated A3 into Context::initialize, and Arguments and A3 will
coexist until A3 surpasses Arguments.
