Fix NLTK Download and add Verbose Flag for GLIP

[Pikus16]

Motivation

Current NLTK download is 1) set in an unexpected directory, and 2) can't be set to quiet with a flag.

Modification

This PR adds both those changes by 1) changing download_dir='~/nltk_data' to download_dir=expanduser('~/nltk_data'), and 2) adding in a verbosity flag to allow to set quiet=True.

BC-breaking (Optional)

No

Use cases (Optional)

If this PR introduces a new feature, it is better to list some use cases here, and update the documentation.

Checklist

1. Pre-commit or other linting tools are used to fix the potential lint issues.
2. The modification is covered by complete unit tests. If not, please add more unit test to ensure the correctness.
3. If the modification has potential influence on downstream projects, this PR should be tested with downstream projects, like MMDet or MMPreTrain.
4. The documentation has been modified accordingly, like docstring or example tutorials.

[CLAassistant]

All committers have signed the CLA.