speculative reorganization of the requirements & environment files

- This is only a test!
- The various environment*.yml and requirements*.txt files have all
  been moved into a directory named "environments-and-requirements".
- The idea is to clean up our root directory so that the github home
  page is tidy.
- The manual install instructions will start with the instructions to
  create a symbolic link from environment.yml to the appropriate file
  for OS and GPU.
- The 1-click installers have been updated to accommodate this change.

.gitignore

@@ -219,3 +219,8 @@ models/gfpgan
 
 # ignore initfile
 invokeai.init
+
+# ignore environment.yml and requirements.txt
+# these are to be copied from environments-and-requirements
+environment.yml
+requirements.txt