GnuCash 2.7.4

What's new in this version:

New Features for Users:
- A new preference panel for the Alphavantage API key so that Finance::Quote users need not edit /etc/gnucash/environment
- On Macs the Reconcile Window's menu moved to the menubar
- The detected Finance::Quote version is displayed in the About box
- Removed all references to the various Yahoo! quote sources and made Alphavantage the default

For Developers and Distro packagers:
- The autotools build system has been removed
- Add a "pot" target to the build system so that translators can easily generate a new gnucash.pot from a git repository
- Improve handling of generated distributable files

Fix make dist on a clean checkout:
- cmake with unix makefiles fails to resolve dist dependencies added from COPY_FROM_BUILD if these dependencies aren't built yet. This commit replaces the COPY_FROM_BUILD based logic with two new functions 'dist_add_configured' and 'dist_add_generated' to indicate which files should be included in the dist tarball. The latter also adds a target level dependency to the dist tarball custom command. Hence the former should be used for files that get generated during a cmake run while the latter should be used for files generated as the result of a 'make/ninja-build' run (like files for which an add_custom_command rule exists). Note: this commit also temporarily disables the dist target when building from a tarball (and hence it won't be tested in distcheck either). This will be handled in a future commit.
- Add DL_LIBS to gncmod-gnome-utils target. Fixes a build problem in FreeBSD.
- Detect presence or absence of libxml2 and makeinfo during configuration; abort if the first is missing and don't build the (mostly obsolete) texinfo documentation if the latter is. Document both in README.dependencies.
- Replaced Timespec with time64 in the Scheme and Python bindings, introducing many new C time64 functions to accomodate the replacement. Timespec will eventually be removed from the C API as well.

Bugs fixed in this release:
- Disabling OFX, AqBanking or python-bindings support cripples the dist build target
- Mathematical bug Actually about the number of weeks from/to 1 Jan 1970.
- 2.7.3: massive test failures on some architectures
- Wrong dates displayed
- Register text difficult to read with GTK 3.0 dark themes Add a foreground css class to override the theme value.
- Missing translatable strings

Some other fixes not associated with reported bugs:
- The long-standing known problem, AQBanking setup crashing on Windows
- Webkit crashing the MacOS Gnucash.app
- Some Guile 2.2 issues are resolved
- Some bugs in the new Transaction Report
- Correct setting of WebKit version during configuration when the version is cached
- The change to the Average Cost calulation introduced in 2.6.12 is reverted
- Fix our appstream id as per the appstream recommendation
- Fix incorrect minimum dates in the net-linechart and net-barchart reports
- Fix a report crash if the Account Depth is too low

Known Problems:
- Unable to overwrite splite3 database file
- There is no Gtk3 theme-setting tool for Windows
- Accounting period dates off-by-1