Improved go-package support and new-project-wizard

In the main branch it was not really possible to run "go build" on folders (whole go packages).
When creating a new project, it is now possible to:
- create a new go-package from a template
- create a new go-package by downloading using "go get"
- specify using radio buttons if the GOPATH should be prepended or appended with the system GOPATH. This allows more project scenarios where it is neccessary to seperate the GOPATH from packages installed in the system GOPATH.

After the creation of a new go project from template or by go get, the wizard will automatically add a RunConfiguration to the project. It is also possible to directly run a go package by right clicking on the corresponding folder.

Some further small changes and bug fixes:
- The "go get" command was added to the SdkUtils.
- The go debugger flags are corrected.
- The GoToolWindow is initialized in case it was not previously opened by the user.
- Moved a global configuration option to the correct settings panel (from project settings to global settings).
- Some GUI descriptions were improved to be better understandable.
- The desired executable name can be specified in the RunConfiguration.
- The standard parameters of RunConfigurations were changed such that debugging of go packages works out of the box.