Refine the context value of the nodes in the project explorer - #311

This PR is to better expose the node context value.

Context Value Format

java:<node type>[+<attribute>]*

Available Node Types:

Currently, available node types are:

• workspaceFolder
• project
• container
• packageRoot
• package
• jar

Not available node types are:

• folder
• file
• type (class, enum, interface,...)

Below picture illustrates the different node types

Attributes:

For each node type, it may have some attributes. Every attribute will start with a +.

Common Attributes:

• +uri: The node has uri

Specific Attributes:

Project Node:

• +java: Java project
• +maven: Maven project
• +gradle: Gradle project

Container Node:

• +jre: Container for JRE
• +maven: Container for Maven
• +gradle: Container for Gradle
• +referencedLibrary: Container for Referenced Libraries

Package Root Node:

• +source: Source package root.
• +resource: Resource package root

Package Node:

• +source: Source package
• +binary: Binary package (Expanded inside a binary jar)

Jar Node:

• +referencedLibrary: Referenced Library jar

Usage example:

For example, A node for a Maven project may have the following context value:

java:project+maven+uri

If you want to register a command on that node, you can write your when clause as:

"when": "view == javaProjectExplorer && viewItem =~ /java:project(?=.*?\\b\\+maven\\b)(?=.*?\\b\\+uri\\b)/",