Separate UIDs and Revisions in main databases

Summary:
- Change revision type from `qint64` to `size_t` for LMDB in a couple of places (LMDB supports `unsigned int` or `size_t` which are `long unsigned int` on my machine)
- Better support for database flags (duplicate, integer keys, integer values for now but is extensible)
- Main databases' keys are now revisions
- Some databases switched to integer keys databases:
  - Main databases
  - the revision to uid mapping database
  - the revision to entity type mapping database
- Refactor the entity type's `typeDatabases` method (if in the future we need to change the main databases' flags again)
- New uid to revision mapping database (`uidsToRevisions`):
  - Stores all revisions (not uid to latest revision) because we need it for cleaning old revisions
  - Flags are: duplicates + integer values (so findLatest finds the latest revision for the given uid)

~~Problems to fix before merging:~~
All Fixed!

- ~~Sometimes Sink can't read what has just been written to the database (maybe because of transactions race conditions)~~
  - ~~Most of the times, this results in Sink not able to find the uid for a given revision by reading the `revisions` database~~
- ~~`pipelinetest`'s `testModifyWithConflict` fails because the local changes are overridden~~

~~The first problem prevents me from running benchmarks~~

Reviewers: cmollekopf

Tags: #sink

Differential Revision: https://phabricator.kde.org/D14974

1 files changed, 3 insertions, 2 deletions

diff --git a/common/storage/key.h b/common/storage/key.h
index baabe38..da90ddd 100644
--- a/common/storage/key.h
+++ b/common/storage/key.h
@@ -67,7 +67,7 @@ public:
     static const constexpr size_t INTERNAL_REPR_SIZE = 19;
     static const constexpr size_t DISPLAY_REPR_SIZE = 19;
 
-    Revision(qint64 rev) : rev(rev) {}
+    Revision(size_t rev) : rev(rev) {}
 
     QByteArray toInternalByteArray() const;
     static Revision fromInternalByteArray(const QByteArray &bytes);
@@ -75,6 +75,7 @@ public:
     QByteArray toDisplayByteArray() const;
     static Revision fromDisplayByteArray(const QByteArray &bytes);
     qint64 toQint64() const;
+    size_t toSizeT() const;
 
     static bool isValidInternal(const QByteArray &);
     static bool isValidDisplay(const QByteArray &);
@@ -84,7 +85,7 @@ public:
     bool operator!=(const Revision &other) const;
 
 private:
-    qint64 rev;
+    size_t rev;
 };
 
 class Key