chore: replace grunt with npm scripts

Grunt's remaining tasks were mostly thin wrappers around tsc, npm test
and npm pack; the rest were small file-manipulation tasks that now live
in scripts/:

- ts:*                              -> tsc (+ tsconfig.release.json)
- clean                             -> scripts/clean.js
- generate/verify unit test deps    -> scripts/generate-test-deps.js
- set_live_ga_id/set_dev_ga_id/...  -> scripts/set-ga-id.js
- template (docs-jekyll)            -> scripts/build-docs.js

prepack now runs the release compile after the tests rather than before,
so removeComments and sourceMap are no longer overwritten by the dev
compile that npm test performs.

Also drops BuildPackage.cmd, last changed in 2014 and calling a grunt
task that no longer exists, and the grunt/globule minimatch overrides,
which no longer resolve to anything in the tree.

Author: edusperoni

.gitignore

@@ -87,5 +87,4 @@ lib/common/test-reports.xml
 !lib/common/test-scripts/**
 !lib/common/scripts/**
 config/test-deps-versions-generated.json
-!scripts/get-next-version.js
-!scripts/get-npm-tag.js
+!scripts/*.js

BuildPackage.cmd

@@ -33,7 +33,7 @@ Before you submit a Pull Request, consider the following guidelines.
 ```bash
     git clone git@github.com:NativeScript/nativescript-cli.git
 ```
-* Run the setup script. This will initialize the git submodule, install the node dependencies and build with grunt.
+* Run the setup script. This will install the node dependencies and set up the git hooks.
 ```bash
     npm run setup
 ```
@@ -44,15 +44,15 @@ Before you submit a Pull Request, consider the following guidelines.
 * Create your patch and include appropriate test cases.
 * Build your changes locally.
 ```bash
-    ./node_modules/.bin/grunt
+    npm run build
 ```
 * Ensure all the tests pass.
 ```bash
-    ./node_modules/.bin/grunt test
+    npm test
 ```
-* Ensure that your code passes the linter.
+* Ensure that your code is formatted.
 ```bash
-    ./node_modules/.bin/grunt lint
+    npm run prettier
 ```
 * Commit your changes following the [commit message guidelines](https://github.com/NativeScript/NativeScript/blob/master/CONTRIBUTING.md#-commit-message-guidelines) (the commit message is used to generate release notes). 
 ```bash

CONTRIBUTING.md

@@ -4,4 +4,4 @@ set -e
 rm -rf docs-cli
 npm install --ignore-scripts
 
-npx grunt docs-jekyll
+npm run docs-jekyll