12/25: Minor bug fixes and specification changes.

[Content Additions & Specification Changes]

1. Changed the image displayed at the end of Endless Battle.
2. Modified the behavior so that if the water is higher than the height when the installation command was given, the water will not be placed upon completion of the installation work. (This change is made to prevent the creation of a water pyramid when trying to place water in a side-by-side arrangement.)

[Bug Fixes]

1. Fixed a bug where cobblestones could be constructed before the relevant technology was acquired.
2. Fixed a bug where new buildings could not be demolished during time stop. (This bug was caused by Unity's special behavior where the collider does not become active when time is set to zero.)