Expose the build command to more places

Below are some feedbacks from user surveys:

• there no build and run feature in a click like netbeans.
• Add a command to rebuild the project the current active file is part of.
• "I really like editing in VS Code but find it not as powerful as tools like Eclipse for build and debug. "
• The burden I got is there was not shortcut for compile java code, it would be awesome if we had it."
• For a maven project I find I have to routinely run "mvn clean compile" after making code changes before it will build.

Actually, we have build action which is called Force Java Compilation, it looks like we need to do some enhancement to expose it to more places. Some ideas:

1. Expose build action to more places (for example, can be invoked in Java Project explorer)
2. Allow to build some of the projects instead of the entire workspace
3. Considering renaming it?? - Because in other IDEs they all call it build, here we call it compilation
4. Ask VS Code to have a dedicate tool bar menu called build or sth...

首先定位现有的 Force Java Compilation 操作，并了解命令如何在 Java Project explorer 和 VS Code UI 中提供。与维护者确定预期范围，然后在构建操作可在约定的位置使用，并且能够针对约定的项目范围时，视为工作完成。