'newt new' should not do shallow copy of blinky repo

[sjanc]

For blinky repo we need full clone as release tag may no longer be on top of master...

[janc@ix test]$ newt new my_proj
Downloading project skeleton from apache/mynewt-blinky...
Downloading repository mynewt-blinky (commit: master) from https://github.com/apache/mynewt-blinky.git
WARNING: Creating a shallow clone by default. To unshallow repository later use "git fetch --unshallow".
Error: error: pathspec 'mynewt_1_10_0_tag' did not match any file(s) known to git

[janc@ix test]$ newt new --shallow=0 my_proj
Downloading project skeleton from apache/mynewt-blinky...
Downloading repository mynewt-blinky (commit: master) from https://github.com/apache/mynewt-blinky.git
Installing skeleton in my_proj (commit: mynewt_1_10_0_rc1_tag)
Project my_proj successfully created.

[sjanc]

after more testing, we should never do shallow by default... this should be opt-in only option