improving script generation and support for Python 3.8+

• Updated deprecated function in web server to support Python 3.8+
• We now use Python to generate ck and ck.bat scripts! If you install CK for different python versions, you can use a specific one as follows:

python3.7 -m ck version

Apache 2.0 license

• We now use Apache 2.0 license based on the feedback from the majority of users
• The code did not change from the last version 1.55.17.
• We plan to focus on incubating projects (see "incubator" directory) to redesign CK and make it simpler, faster and more Pythonic - we plan to use version 3.x for the new design.

fixed major bug and added MLPerf tests

• fixed a bug in module:env.
• added more MLPerf tests from https://github.com/ctuning/ck-ml to find above bug.
• added detection of packages with problems to print notes about how to solve them (useful for ImageNet 2012 packages where direct download is no longer available).

added LICENSE.third-party.txt and module:docs

• added module:docs to be more compatible with standard repos
• added LICENSE.third-party.txt

improved error reporting

• improved error reporting in packages and programs
• print "Enter -1 to use CK packages" when detecting soft to install CK packages instead of detecting already installed software

A few extensions

• Added module:doc to the distribution
• Test environment variable "CK_SKIP_SAVING_PYTHON_BIN" during CK installation
  to skip detecting and recording python binary to ck-python.cfg
  to avoid mixing up virtual environments.
• When CK_PYTHON is defined during CK installation,
  record it to ck-python.cfg to preserve the default version.

Improving package installation

Important change: do not ask to select variations in "ck install package" when there are 2 or more variations!
Needed to distinguish between selecting different versions of a given package or customizing the same package!

added --force_version to "ck detect soft"

Added --force_version to "ck detect soft" to force version.
Useful to automate autodetection of imagenet, for example.

added --quiet to install packages

• added --quiet flag to automatically enter default answer to most questions

added --default flag to the package module

• added --default flag to ck install package to automatically select 0 when multiple packages and variations available.