pt_BR: update translation (#814)

Split off translatable strings (integral approach) (#813)

* Split off translatable strings in source code and translation template

* Split off translatable strings in translation files

Shell command on macOS:
for i in de fr_FR it pt_BR ru_RU zh_CN; do cd $i; sed -Ibak -E 's/"(.*)\\t.*"/"\1"/g' ts.po; cd ..; done

* Remove duplicates from the translation files

On the macOS shell:
for i in de fr_FR it pt_BR ru_RU zh_CN; do cd $i; msguniq ts.po -o ts.po --use-first; cd ..; done

* Merge the changes from the translation template into the translation files

* Adapt the German translation

* Compile the German translation

Attempt to fix new broken GCC warnings

Add key binding for Turn filter off (#805)

Improve grammar when there is just one cell/char (#808)

* Improve grammar when there is just one cell/char

* Revert change in line 355 of `src/system.h`

Add translatable help strings to menu entries (#807)

Default to build against distribution wxWidgets (#801)

Revert dynamic datastructures (#804)

* Revert "Avoid double ownership (#800)"

This reverts commit 89b40de.

* Revert "Fix bad unique_ptr usage"

This reverts commit 2086ce8.

* Revert "Use correct method to delete resource (#783)"

This reverts commit 81e74a0.

* Revert "Use unique_ptr for Grid in Cell (#782)"

This reverts commit 9fe088a.

* Revert "Make rootgrid an unique_ptr (#776)"

This reverts commit 15d5f58.

* Revert "Use vector instead of raw pointer arrays (#785)"

This reverts commit 9dfc4fb.

* Revert "Use unique_ptr for Document in TSCanvas (#780)"

This reverts commit e3d4602.

Avoid double ownership (#800)

Do not trigger reset on DPI change on macOS platform (#795)

It is not necessary on macOS and moreover creates a segmentation fault.

AddressSanitizer:DEADLYSIGNAL
=================================================================
==16564==ERROR: AddressSanitizer: SEGV on unknown address 0xffffd847d7d9d7db (pc 0x000104f52700 bp 0x00016af19a50 sp 0x00016af199c0 T0)
==16564==The signal is caused by a READ memory access.
    #0 0x104f52700 in treesheets::Cell::Reset() cell.h:307
    #1 0x104f51ef8 in treesheets::Cell::ResetChildren() cell.h:309
    #2 0x104ee90d8 in treesheets::MyFrame::OnDPIChanged(wxDPIChangedEvent&) myframe.h:1154
    #3 0x105ebd0d4 in wxAppConsoleBase::HandleEvent(wxEvtHandler*, void (wxEvtHandler::*)(wxEvent&), wxEvent&) const appbase.cpp:644
    #4 0x105ebd4a0 in wxAppConsoleBase::CallEventHandler(wxEvtHandler*, wxEventFunctor&, wxEvent&) const appbase.cpp:656
    #5 0x10624324c in wxEvtHandler::ProcessEventIfMatchesId(wxEventTableEntryBase const&, wxEvtHandler*, wxEvent&) event.cpp:1456
    #6 0x106242b4c in wxEventHashTable::HandleEvent(wxEvent&, wxEvtHandler*) event.cpp:1061