Adopt hexbox under Debian .NET Team (1.5.0+dfsg-2)

Adoption upload, closes ITS #1137416.

This MR adopts hexbox under the Debian .NET Team and addresses a CRLF patch incompatibility that had accumulated in the package.

The upstream .csproj files use Windows CRLF line endings. dpkg-source strips trailing CRs from patch text before application, which causes three of the four existing quilt patches to fail with "different line endings". The fix treats it as a data-transformation problem rather than a patch problem: the two functional patches are replaced with a build-time Python script (debian/remove-localized-resources.py) and a sed one-liner in debian/rules respectively; a third patch is dropped as redundant since debian/rules already passes the equivalent flag to xbuild on the command line; and bug767355.patch is kept as it applies cleanly.

The Python script uses binary read/write to guarantee CRLF preservation on disk, an atomic tmp+rename write to protect against interrupted builds, and exits 0 if no blocks are found so incremental rebuilds without clean do not fail.

Other changes: Maintainer set to Debian .NET Team, Uploaders to James Montgomery; Standards-Version 4.7.4; Multi-Arch: foreign for libhexbox1.5-cil; dh_fixperms override to strip the executable bit from the DLL; Upstream-Sources corrected to Upstream-Source in copyright; spurious leading slash removed from monodoc .install paths; debian/gbp.conf added.

QA: lintian clean on .dsc; .changes shows only expected UNRELEASED warnings and one pre-existing no-manual-page. piuparts PASS. cme check dpkg clean. Built with sbuild against unstable.