Update some copyright strings and drop __revision__ [skip appveyor]

Touches the first and second levels of SCons (except SCons.Tool),
not tests or docs which remain TODO.

Make sure docstring is first non-comment content, eliminate cases where
docstring is set elsewhere but assigns to __doc__ - this approach of
course worked inside Python, but confuses various tools.

Some module-level docstrings modified a bit, in particular
the convention of having the name of the module as the first line
is dropped, replaced by a summary description going there instead -
this improves the look in the API Docs, which otherwise display
something like:
  SCons.Foo - SCons.Foo

Signed-off-by: Mats Wichmann <mats@linux.com>

1 files changed, 23 insertions, 0 deletions

diff --git a/SCons/__main__.py b/SCons/__main__.py
index 0dfbb9d..67120c8 100644
--- a/SCons/__main__.py
+++ b/SCons/__main__.py
@@ -1,3 +1,26 @@
+# MIT License
+#
+# Copyright The SCons Foundation
+#
+# Permission is hereby granted, free of charge, to any person obtaining
+# a copy of this software and associated documentation files (the
+# "Software"), to deal in the Software without restriction, including
+# without limitation the rights to use, copy, modify, merge, publish,
+# distribute, sublicense, and/or sell copies of the Software, and to
+# permit persons to whom the Software is furnished to do so, subject to
+# the following conditions:
+#
+# The above copyright notice and this permission notice shall be included
+# in all copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY
+# KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
+# WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+# LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+# OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+# WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+
 import SCons.Script
 # this does all the work, and calls sys.exit
 # with the proper exit status when done.