Resolve sign conversion warnings - prefetch preference

Resolve warnings that occur when building w/ ALL_WARNINGS enabled. Source tree
examined to enusre prefetch size is handled as type std::size_t. Also, tree was
modified correcting handling of the chunkSize variable in sqlitetablemodel that
uses the prefetch preference setting.

Also, some minor editing of sources was taken to improve readability
as well as consistency.

Update version number to 3.11.2

The rebuilt macOS installer (v2) was generated from this tag.

Update version number to 3.11.1

We're using Qt 5.11.3 for the Win64 builds

The DB4S 3.11.0-beta3 Win32/64 & macOS binaries were created from

this commit.

The DB4S 3.11.0-beta2 Win32/64 & macOS binaries were created from thi…

…s commit.

The DB4S 3.11.0-beta1 Win32/64 & macOS binaries were

created from this commit.

This commit is what the DB4S 3.11.0-alpha1 Win32/64 & macOS binaries …

…were created from.

Update version numbers to 3.10.1