Remove std::.
Import directive.
Multi-source and multi-contract compiler.
Improved external interface for multi-source and multi-contract compilation.
Merge remote-tracking branch 'ethereum/develop' into sol_import

Conflicts:
	libsolidity/CompilerStack.cpp
	libsolidity/CompilerStack.h
	solc/main.cpp
Renamed url to identifier and added some comments.
Comments and braces.
Merge remote-tracking branch 'ethereum/develop' into sol_import

Conflicts:
	libsolidity/CompilerStack.cpp
	libsolidity/CompilerStack.h
	libsolidity/InterfaceHandler.cpp
	libsolidity/InterfaceHandler.h
	solc/main.cpp
	test/solidityJSONInterfaceTest.cpp
	test/solidityNatspecJSON.cpp
Merge pull request #558 from chriseth/sol_import

Solidity for multiple files and multiple contracts per file.