Independent builds and python support

This MR introduces various features:

1. This package is now built completely independently of the bob software stack (and bob.conda). It ships its own version of dependencies and can provide better support for python versions that are not necessarily supported (yet) by Bob or BEAT
2. As a bonus, you can now install this package alongside your conda base environment
3. An optimisation during the bootstrap process is now possible since we don't need to install a new environment for bdt using python-3.6, it can just install in the base environment itself.
4. This MR also makes git-clean a bit less verbose, on request form @amohammadi
5. Finally, it fixes #13 (closed), as reported by @heusch

bob/devtools/data/gitlab-ci/single-package.yaml

@@ -20,9 +20,9 @@ stages:
   stage: build
   script:
     - curl --silent "${BOOTSTRAP}" --output "bootstrap.py"
-    - python3 bootstrap.py -vv channel bdt
+    - python3 bootstrap.py -vv channel base
     - source ${CONDA_ROOT}/etc/profile.d/conda.sh
-    - conda activate bdt
+    - conda activate base
     - bdt ci build -vv
     - bdt ci clean -vv
   cache: &build_caches
@@ -66,9 +66,9 @@ build_linux_36:
     BUILD_EGG: "true"
   script:
     - curl --silent "${BOOTSTRAP}" --output "bootstrap.py"
-    - python3 bootstrap.py -vv channel bdt
+    - python3 bootstrap.py -vv channel base
     - source ${CONDA_ROOT}/etc/profile.d/conda.sh
-    - conda activate bdt
+    - conda activate base
     - bdt ci build -vv
     - bdt ci readme -vv dist/*.zip
     - bdt ci clean -vv
@@ -91,9 +91,9 @@ build_macosx_36:
   stage: deploy
   script:
     - curl --silent "${BOOTSTRAP}" --output "bootstrap.py"
-    - python3 bootstrap.py channel bdt
+    - python3 bootstrap.py channel base
     - source ${CONDA_ROOT}/etc/profile.d/conda.sh
-    - conda activate bdt
+    - conda activate base
     - bdt ci deploy -vv
     - bdt ci clean -vv
   dependencies:
@@ -133,9 +133,9 @@ pypi:
     - branches
   script:
     - curl --silent "${BOOTSTRAP}" --output "bootstrap.py"
-    - python3 bootstrap.py -vv channel bdt
+    - python3 bootstrap.py -vv channel base
     - source ${CONDA_ROOT}/etc/profile.d/conda.sh
-    - conda activate bdt
+    - conda activate base
     - bdt ci pypi -vv dist/*.zip
     - bdt ci clean -vv
   dependencies: