continue development of vwml battle project
1. add 'external' keyword to grammar in order to have ability to define visibility of contexts defined in another modules
2. assemble entity during dynamic addressing (complex entity assembling)
3. continue development of battle
1. continue development of first stage of battle simulator
2. allowing extended syntax after 'Exe' operation, like this: <term> Exe <operation> (a~ Exe [)
Merge branch 'origin/master'