Infinite Scroll overwrites default views content classes and existing theme wrappers

Problem/Motivation

views_infinite_scroll_preprocess_views_view() overwrites any existing #theme_wrappers and attributes (including default views classes), causing incompatibility with other modules, complicating theming, etc.

Scenario 1: Using the "Views Bulk Operations" module

Steps for reproducing:

1. Enable the "Views Bulk Operations" module
2. Add and configure a bulk operations field
3. Confirm that bulk operations can be applied to selected view rows/results
4. Configure the view to use an Infinite Scroll pager
5. Attempt to apply bulk operations to selected view rows/results

Expected result:
Bulk operations are applied as before.

Actual result:
No action occurs.

Scenario 2: Using the "Blazy Grid" view format

Steps for reproducing:

1. Create a view with format "Blazy Grid"
2. Check grid structure; note that grid has classes like "blazy blazy--grid block-column block-count-8 blazy--on"
3. Configure the view to use an Infinite Scroll pager
4. Check grid structure

Expected result:
Grid has classes like "blazy blazy--grid block-column block-count-8 blazy--on"

Actual result:
Grid has only these classes: "views-infinite-scroll-content-wrapper clearfix'"

Proposed resolution

Update views_infinite_scroll_preprocess_views_view() so it applies the necessary container and attributes in a non-destructive way.

Remaining tasks

Review/test the patches below.

User interface changes

None.

API changes

None.

Data model changes

None.