Boost.Build Python port overall status

What works

• Interface between Python and Boost.Jam build engine is finished.
• Project loading and target declaration works
• Top-level code is ported, including getting build request, loading configuration files and projects and building/cleaning.
• A simple project with a 'make' rule loads and builds fine

Status of porting code modules

The below table documents the state of files in the 'build' directory. There, 'done' means the file is totally done, 'almost' means the file is essentially done, but maybe we tweaks are necessary as other files are ported and 'pending' is not yet there.

File	Lines	Status	Notes
targets.jam	1550	almost
feature.jam	1284	pending
virtual-target.jam	1231	almost	Need to fix dependency properties
generators.jam	1214	pending
project.jam	1018	pending
property.jam	694	pending
toolset.jam	510	pending
property-set.jam	464	pending
type.jam	370	pending
build-request.jam	301	pending
modifiers.jam	241	pending
scanner.jam	151	pending
alias.jam	75	done
version.jam	20	pending

Status of porting tools

We'll start by porting gcc, and proceed to other compilers only when all tests pass with gcc.

Post port: code cleanup

After all tests are passing with gcc, the following cleanups are desired:

• Convert all modules still using global variables to using 'context' object.
• Introduce Property class, and no longer store properties as specially formatted strings

Post port: design cleanup

• Use 'Metatarget' prefix for classes in the 'target' module
• Kill ProjectAttributes and keep all information about project inside ProjectTarget