check-seclevel: set executable bit as it has shebang

bundle20: extract core payload generation in its own function We are about to allow compressing the core of the bundle2. So we extract the generation of this bits in its own parts to make this compression phases easier in a later changesets.

unbundle20: allow registering handlers for stream level parameters As a comment in the code have been asking for, it is now possible to register piece of code that handle parameters for the stream. I've been wondering is such function should be class methods or not. I eventually went for externally decorated methods to stick with the culture of extensibility from an extensions that apply to bundle2.

bundle2: allow to specify unsupported value on error A client may support an argument but not some of its values (eg: coming "compression" parameters). We allow this case to be carried in the exception.

bundle2: rename error exception class for unsupported feature The original name explicitly mention "Part", however it is also used outside of parts related feature. We rename from 'UnsupportedPartError' to 'BundleUnknownFeatureError' to fix this.

changegroup: use a different compression key for BZ in HG10 For "space saving", bundle1 "strip" the first two bytes of the BZ stream since they always are 'BZ'. So the current code boostrap the uncompressor with 'BZ'. This hack is impractical in more generic case so we move it in a dedicated "decompression".

monoblue: provide links to branches, tags and bookmarks by name This is adapted from cd842821db2c, that was added to paper for 3.5 release. It adds another way to refer to branches, tags and bookmarks in urls: by name. It's still possible to navigate to a specific changeset hash, but now you can get more descriptive urls straight from /summary page, for example. branchentry template (and so the whole branches table on /summary and /branches) lost the column that had a plain changeset hash, because tags and bookmarks don't have this column and also because there is already a way to address branch by its changeset hash (changeset link just next to it). Maybe we can instead bring this column with a plain changeset hash to tags and bookmarks, but this, more terse, new look feels fine.

gitweb: provide links to branches, tags and bookmarks by name This is adapted from cd842821db2c, that was added to paper for 3.5 release. It adds another way to refer to branches, tags and bookmarks in urls: by name. It's still possible to navigate to a specific changeset hash, but now you can get more descriptive urls straight from /summary page, for example. branchentry template (and so the whole branches table on /summary and /branches) lost the column that had a plain changeset hash, because tags and bookmarks don't have this column and also because there is already a way to address branch by its changeset hash (changeset link just next to it). Maybe we can instead bring this column with a plain changeset hash to tags and bookmarks, but this, more terse, new look feels fine.

cmdutil: remove HG: prefix from translation strings

i18n-zh_CN: annotate broken HG: translations