Indent snippet new line if LSP client doesn't support `InsertTextMode#AdjustIndentation`

[angelozerr]

In Eclipse IDE, the snippet section doesn't generate correctly the line identation (for new ines)

After reading microsoft/language-server-protocol#83, I noticed that Eclipse IDE doesn't support InsertTextMode#AdjustIndentation, it means that we need to check this mode (coming from LSP client capability) and generate the proper line indentation in this case.